Method for producing oligomers derived from butenes

ABSTRACT

The present invention relates to a process for preparing oligomers consisting mainly of repeating units derived from 1- or 2-butene from a hydrocarbon stream consisting substantially of branched and linear hydrocarbon compounds having 4 carbon atoms, and comprising olefinic branched and linear hydrocarbon compounds having 4 carbon atoms (C 4  starting stream) by 
     a. in step a), separating the C 4  starting stream into a fraction consisting mainly of linear hydrocarbon compounds having 4 carbon atoms (l-C 4  fraction) and a fraction consisting mainly of branched hydrocarbon compounds having 4 carbon atoms (b-C 4  fraction), by contacting the C 4  starting stream with a membrane which is easier to pass for linear hydrocarbon compounds having 4 carbon atoms than for branched hydrocarbon compounds having 4 carbon atoms,    b. in step b), optionally after removing butanes, oligomerizing the olefinic hydrocarbon compounds having 4 carbon atoms present in the l-C 4  fraction,    c. in step c), subjecting the olefinic hydrocarbon compounds having 4 carbon atoms present in the b-C 4  fraction to one of the following steps: c1. reaction with methanol to give methyl tert-butyl ether (step c1) c2. hydroformylation to give substantially isovaleraldehyde (step c2) c3. polymerization to polyisobutylene (step c3) c4. dimerization to 2,4,4-trimethyl-1-pentene (step c4) c5. alkylation, substantially to form saturated hydrocarbon compounds having 8 or 9 carbon atoms (step c5).

The present invention relates to a process for preparing oligomersconsisting mainly of repeating units derived from 1- or 2-butene from ahydrocarbon stream consisting substantially of branched and linearhydrocarbon compounds having 4 carbon atoms, and comprising olefinicbranched and linear hydrocarbon compounds having 4 carbon atoms (C₄starting stream) by

-   a. in step a), separating the C₄ starting stream into a fraction    consisting mainly of linear hydrocarbon compounds having 4 carbon    atoms (l-C₄ fraction) and a fraction consisting mainly of branched    hydrocarbon compounds having 4 carbon atoms (b-C₄ fraction), by    contacting the C₄ starting stream with a membrane which is easier to    pass for linear hydrocarbon compounds having 4 carbon atoms than for    branched carbon compounds having 4 carbon atoms,-   b. in step b), optionally after removing butanes, oligomerizing the    olefinic hydrocarbon compounds having 4 carbon atoms present in the    l-C₄ fraction,-   c. in step c), subjecting the olefinic hydrocarbon compounds having    4 carbon atoms present in the b-C₄ fraction to one of the following    steps:    -   c1. reaction with methanol to give methyl tert-butyl ether (step        c1)    -   c2. hydroformylation to give substantially isovaleraldehyde        (step c2)    -   c3. polymerization to polyisobutylene (step c3)    -   c4. dimerization to 2,4,4-trimethyl-1-pentene (step c4)    -   c5. alkylation, substantially to form saturated hydrocarbon        compounds having 8 carbon atoms (step c5).

Processes for preparing oligomers, in particular octenes and dodecenes,derived from butenes are common knowledge.

The octenes or dodecenes generally serve as starting products for thepreparation of alcohols which are obtainable from the starting productsby hydroformylation and subsequent hydrogenation. The alcoholsfrequently find use in the preparation of plasticizers or surfactantalcohols.

For the use as plasticizer alcohol, the degree of branching plays adecisive role for the properties of the plasticizer. The degree ofbranching is described by the iso index which expresses the averagenumber of methyl branchings in a particular fraction. For example,n-octenes with 0, methylheptenes with 1 and dimethylhexenes with 2contribute to the iso index of a C₈ fraction. The lower the iso index,the more linear the construction of molecules in the particularfraction. The higher the linearity, i.e. the lower the iso index, thehigher the yields in the hydroformylation and the better the propertiesof the plasticizer produced therefrom. A low iso index, for example inthe case of phthalate plasticizers, has a favorable effect with regardto low volatility and better cold crack temperature of the plasticizedPVC produced with the plasticizer.

Processes for preparing unbranched octene or dodecene are disclosed, forexample, by WO 9925668 and 0172670.

In order to be able to obtain the desired plasticizers with the low isoindex, the starting materials required for the preparation of theoctenes or dodecenes are olefinic C₄ hydrocarbon fractions whichcomprise a very low proportion of branched C₄ hydrocarbons.

As a consequence of the very close boiling points, the separation ofbranched and linear olefinic hydrocarbon compounds having 4 carbon atomscan be carried out distillatively only with difficulty. For this reason,it has been proposed to react the isobutene under conditions under which1- and 2-butene behave substantially inertly and to remove the reactionproduct.

Suitable for this purpose are, for example, a) the reaction withmethanol to give methyl tert-butyl ether (MTBE) or the Lewis-acidcatalyzed polymerization to polyisobutylene (cf. Industrielle OrganischeChemie, K. Weissermel, H.-J. Arpe, Verlag Wiley-VCH, 1998, 5th Edition,Chapter 3.3.2.)

It is also known (loc. cit.) that linear hydrocarbon compounds having 4carbon atoms are selectively absorbed on certain molecular sieves, thusallowing separation of isobutene to be achieved.

EP-A-481660 states that membranes having a zeolite structure aresuitable for the separation of n-butanes from isobutane.

It is an object of the present invention to provide a process whichenables a) the preparation of substantially unbranched octene anddodecene from a fraction comprising both linear and branched olefinichydrocarbon compounds having 4 carbon atoms and b) the simultaneouspreparation of various chemical intermediates which are derived fromisobutene in high yields.

We have found that this object is achieved by the invention defined atthe outset.

The starting stream generally consists of

-   -   from 30 to 99%, preferably from 40 to 96%, more preferably from        50 to 70% by weight of olefinic branched and linear hydrocarbon        compounds having 4 carbon atoms (C₄ ⁼fraction)    -   preferably from 5 to 55% by weight of saturated branched and        linear hydrocarbons having 4 carbon atoms (C₄ ⁻fraction)    -   optionally up to 50%, preferably up to 5% by weight of other        unsaturated hydrocarbon compounds having 4 carbon atoms    -   optionally up to 50%, preferably up to 5% by weight of        hydrocarbon compounds having less than 4 or more than 4 carbon        atoms.

In general, the sum of olefinic branched and linear hydrocarboncompounds having 4 carbon atoms and saturated linear and branchedhydrocarbon compounds having 4 carbon atoms in the total amount of theC₄ starting stream is at least 30%, preferably 50% by weight.

The other unsaturated hydrocarbon compounds having 4 carbon atoms aregenerally butadienes, alkynes or allenes.

The hydrocarbon compounds having less than 4 or more than 4 carbon atomsare preferably propane, propene, pentanes, pentenes, hexanes or hexenes.

In general, the C₄ starting stream is prepared by carrying out thefollowing sequence of steps:

-   -   removing a C₄ hydrocarbon fraction (C₄ stream) from a        hydrocarbon stream from natural sources or obtainable by        subjecting naphtha or other streams which comprise hydrocarbon        compounds to a steam cracking or FCC process,    -   preparing a C₄ hydrocarbon stream (raffinate l) consisting        substantially of isobutene, 1-butene, 2-butene and butanes from        C₄ stream by hydrogenating the butadienes and butynes to        C₄-alkenes or C₄-alkanes by means of selective hydrogenation or        removing the butadienes and butynes by extractive distillation,    -   freeing raffinate l of catalyst poisons by treating with        adsorbent materials and in this way obtaining C₄ starting        stream.

If desired, the raffinate l can be used in step a) without precedingremoval of catalyst poisons. In this case, the removal of the catalystpoisons is carried out immediately after step a).

C₄ stream is prepared, for example, from LPG or LNG streams. LPG meansLiquefied Petroleum Gas (liquid gases). Such liquid gases are defined,for example, in DIN 51 622. They generally comprise the hydrocarbonspropane, propene, butane, butenes and their mixtures, as obtained in oilrefineries as by-products in distillation and cracking of crude oil andalso in the benzene separation in the course of natural gas processing.LNG means Liquefied Natural Gas. Natural gas consists mainly ofsaturated hydrocarbons which, depending on their origin, have differentcompositions and are generally divided into three groups. Natural gasfrom pure natural gas deposits consists of methane and a little ethane.Natural gas from crude oil deposits additionally comprises relativelylarge amounts of higher molecular weight hydrocarbons such as ethane,propane, isobutane, butane, hexane, heptane and by-products. Natural gasfrom condensate and distillate deposits comprises not only methane andethane, but also, to a considerable extent, higher-boiling componentshaving more than 7 carbon atoms. For a more detailed description ofliquid gases and natural gas, reference may be made to the appropriatekeywords in Römpp, Chemielexikon, th Edition.

The LPG and LNG used as a feedstock comprises in particular fieldbutanes, as the C₄ fraction of the “moist” fractions of natural gas andalso the accompanying crude oil gases are known, which are removed fromthe gases in liquid form by drying and cooling to about −30° C. Thefield butanes, whose composition varies depending on the deposit, butwhich generally contain about 30% of isobutane and about 65% ofn-butane, are obtained therefrom by low temperature or pressuredistillation.

It is also possible to obtain the C₄ stream by subjecting naphtha orother hydrocarbon compounds to a steam cracking or FCC process anddistillatively removing the C₄ stream from the hydrocarbon productsformed.

In the generally known FCC process (cf. Ullmann's Encyclopedia ofIndustrial Chemistry, Wiley-VCH Verlag GmbH, Weinheim, Germany, SixthEdition, 2000 Electronic Release, Chapter Oil Refining, 3.2. CatalyticCracking), the appropriate hydrocarbon is evaporated and contacted inthe gas phase with a catalyst at a temperature of from 450 to 500° C.The particulate catalyst is fluidized by the hydrocarbon streamconducted in countercurrent. The catalysts used are customarilysynthetic crystalline zeolites.

In the likewise generally known steam cracking process (cf. A. Chauvel,G. Lefebvre: Petrochemical Processes, 1 Synthesis-Gas Derivatives andMajor Hydrocarbons, 1989 Editions Technip 27 Rue Ginoux 75737 Paris,France, Chapter 2), the hydrocarbon is mixed with steam and, dependingon the residence time, heated in tubular reactors to temperatures offrom 700 to 1200° C. and afterwards cooled rapidly and distillativelyseparated into individual fractions.

The raffinate l can be obtained from the C₄ stream by removing orpartially hydrogenating the dienes, alkynes and enynes.

Preference is given to carrying out the substep of butadiene extractionfrom crude C₄ cut with a butadiene-selective solvent selected from theclass of polar aprotic solvents, such as acetone, furfural,acetonitrile, dimethylacetamide, dimethylformamide andN-methylpyrrolidone.

Preference is given to carrying out the substep of selectivehydrogenation of butadiene and acetylenic impurities present in the C₄stream in two stages by contacting the crude C₄ cut in the liquid phasewith a catalyst which comprises at least one metal selected from thegroup of nickel, palladium and platinum, on a support, preferablypalladium on aluminum oxide, at a temperature of from 20 to 200° C., apressure of from 1 to 50 bar, a catalyst hourly space velocity of from0.5 to 30 m³ of fresh feed per m³ of catalyst per hour and a ratio ofrecycle to feed stream of from 0 to 30 at a molar ratio of hydrogen todiolefins of from 0.5 to 50, in order to obtain a reaction effluent inwhich, in addition to isobutene, the n-butenes 1-butene and 2-butene arepresent in a molar ratio of from 2:1 to 1:10, preferably from 2:1 to1:2, and substantially no diolefins or acetylenic compounds are present.

The raffinate l stream is generally purified over at least one guard bedconsisting of high-surface-area aluminum oxides, silica gels,aluminosilicates or molecular sieves. The guard bed serves to dry theraffinate l stream and also to remove substances which can act ascatalyst poison in one of the subsequent conversion steps. The preferredadsorber materials are Selex-sorb CD and CDO, and also 3 Å and NaXmolecular sieves (13×). The purification is effected in drying towers attemperatures and pressures which are selected in such a way that allcomponents are in the liquid phase.

When the catalyst poisons are removed immediately after step a), thel-C₄ and b-C₄ fractions are treated in a similar manner.

The separation in step a can be carried out by membrane processes knownper se (cf. EP-A-481660). Useful membrane materials are, for example,polymers or inorganic materials having molecular sieve properties. Thelatter are, for example, prepared by pyrolysis of organic polymers suchas polypropylene or are zeolites, for example those of the MFI type suchas silicalite of the ZSM-5 type.

The membranes are preferably configured as integrally symmetrical or ascomposite membranes in which the actual separating layer effecting themolecular separation which has a thickness of from 0.1 to 100 μm,preferably from 1 to 20 μm, is applied to one or more meso- and/ormacroporous supports.

The membranes are used in the form of flat, pillow, capillary,monochannel tubular or multichannel tubular elements, which are knownper se to those skilled in the art from other membrane separatingprocesses such as ultrafiltration or reverse osmosis. In the case ofmembrane elements having tubular geometry, the separating layer ispreferably disposed on the inside of the tube.

The membranes are generally surrounded by one or more casings ofpolymeric, metallic or ceramic material, and the connection betweencasing and membrane is formed by a sealing polymer (for exampleelastomer) or inorganic material.

The membrane process is customarily operated in such a way that the C₄starting stream in liquid or gaseous form is contacted with the membraneand the l-C₄ fraction passing the membrane is removed in gaseous form,and the pressure on the side of the membrane on which the C₄ startingstream is disposed (feed side) is greater than the pressure on the sideof the l-C₄ fraction (permeate side). The temperature at which themixture to be separated is contacted with the membrane is typicallybetween 20 and 200° C., preferably from 50 to 150° C. The pressure onthe feed side of the membrane is advantageously from 1 to 100 bar abs.,preferably from 2 to 40 bar abs., and is generated by mechanicalcompression or pumps and heating of the feed stream to a temperaturewhich leads to a vapor pressure of the feed mixture corresponding to thedesired feed pressure. The pressure on the permeate side is from 0.1 to50 bar, preferably from 0.5 to 10 bar, and the pressure on the feed sideis always higher than that on the permeate side. The pressure on thepermeate side is set by removing the permeate stream by means of avacuum pump or of a compressor or by condensing the permeate stream at atemperature which leads to an autogenous pressure on the permeatemixture corresponding to the desired permeate pressure.

One way of performing the membrane process is in one stage, i.e. thepermeate from a membrane apparatus or the combined permeates from aplurality of membrane apparatus flowed through by the feed in seriesand/or parallel, without further treatment, forms the linearhydrocarbon-enriched l-C₄ fraction mentioned and the nonpermeatedfraction (retentate), without further treatment, forms thebranched-hydrocarbon-enriched b-C₄ fraction mentioned. However, themembrane process may also be carried out in two or more stages, byconducting the permeate from one stage as the feed into the followingstage in each case and mixing the retentate from this stage with thefeed into the former stage. Such arrangements are known per se (see, forexample, Sep.Sci.Technol. 31 (1996), 729 ff).

The separating process achieves a proportion of the l-C₄ fraction in theb-C₄ fraction and a proportion of the b-C₄ fraction in the l-C₄ fractionof from 10 ppm by weight to 30% by weight, preferably from 1000 ppm byweight to 25% by weight, more preferably from 1 to 20% by weight.

In step b, in which the oligomerization of the l-C₄ fraction is carriedout, preference is given to preparing mainly octenes and dodecenes overnickel catalysts.

Octenes and dodecenes constitute valuable intermediates which can inparticular be converted by hydroformylation and subsequent hydrogenationto nonanol and tridecanol respectively.

It has proven advantageous to partly distillatively remove n-butane fromthe l-C₄ fraction after step a. The l-C₄ fraction used in step bpreferably contains not more than 30% by weight, more preferably 15% byweight, of n-butane.

Useful nickel catalysts are in particular those nickel-containingcatalysts which are known to promote little oligomeric branching, cf.,for example, prior art references cited in DE 4339713 and WO 01/37989,and these references in particular relating to the catalysts areexplicitly incorporated herein by way of reference. Particularpreference is given to catalysts which comprise both sulfur and nickelas active components.

Very particular preference is given to combining catalysts which differin the S:Ni ratio. Advantageously, the catalyst used in the firstreaction stage has an S:Ni ratio of <0.5 mol/mol, and is preferably acatalyst according to WO 01/37989 or DE 4339713, and the catalyst usedin the second reaction stage has an S:Ni ratio of >0.5 mol/mol, and ispreferably a catalyst according to EP 272970, U.S. Pat. No. 3,959,400,FR 2641477 or U.S. Pat. No. 4,511,750 having an S:Ni ratio of >0.8, morepreferably 1.0.

The abovementioned catalysts may be used, for example, in processes asdescribed, for example, in WO 99125668 and WO 01/72670, which areexplicitly incorporated herein by way of reference.

When the nickel catalyst in the reactor is disposed in a plurality offixed beds, the feed may be introduced into the reactor divided and at aplurality of points, for example upstream of a first fixed bed in theflow direction of the reaction mixture and/or between individual fixedNi catalyst beds. When a reactor battery is used, it is possible, forexample, to feed the feed completely to the first reactor of the batteryor to feed it to the individual reactors of the battery through aplurality of feeds, as described for the case of the single reactor.

The oligomerization reaction generally takes place at temperatures offrom 30 to 280, preferably from 30 to 190 and in particular from 40 to130° C., and a pressure of generally from 1 to 300 bar, preferably from5 to 100 bar and in particular from 10 to 50 bar. The pressure isadvantageously selected in such a way that the feed is supercritical andespecially liquid at the temperature set.

The reactor is generally a cylindrical reactor charged with the Nicatalyst; alternatively, a battery of a plurality, preferably two orthree, such reactors connected in series can be used.

In the reactor or the individual reactors of the reactor battery, thenickel catalyst may be disposed in a single or in a plurality of fixednickel catalyst beds. It is also possible to use different nickelcatalysts in the individual reactors of the battery. It is also possibleto set different reaction conditions in the individual reactors of thereactor battery with regard to pressure and/or temperature within theabovementioned pressure and temperature ranges.

The first reaction stage should be operated at >50%, preferably >70% andmore preferably >90%, overall olefin conversion, while the secondreaction stage should ensure the remaining conversion, so that a totaloverall olefin conversion of >91%, preferably >95% and morepreferably >97% results. This is in principle also possible using thecatalyst of the first reaction stage alone, although it would require,in comparison to the invention, either high reaction temperatures whichlead to relatively rapid catalyst deactivation, or large catalystvolumes which would put into question the economic viability of theprocess.

Both the first and the second reaction stage may each consist of one ormore reactors connected in series, as described in WO 99/25668 or01/72670.

The isobutene-rich b-C₄ fraction is further converted by one of the 5following processes, i.e. the entire amount of the b-C₄ fraction isfurther converted by only one of these processes, or proportions of thisfraction can also be further converted each by different processes.

MTBE is prepared from methanol and the isobutene-rich b-C₄ fraction instep c.1 generally at from 30 to 100° C. and slightly elevated pressurein the liquid phase over acidic ion exchangers. It is customary to workeither in two reactors or in a two-stage shaft reactor, in order toachieve virtually complete isobutene conversion (>99%). To prepare pureMTBE, the pressure-dependent azeotrope formation between methanol andMTBE entails multistage pressure distillation or is achieved byrelatively new technology by methanol adsorption on adsorber resins. Allother components of the C₄ fraction remain unchanged. Since smallamounts of diolefins and acetylenes can shorten the lifetime of the ionexchanger by polymer formation, preference is given to usingbifunctional PD-containing ion exchangers, in which case only diolefinsand acetylenes are hydrogenated in the presence of small amounts ofhydrogen. The etherification of isobutene is unaffected.

The preparation of MTBE can also be carried out in a reactivedistillation (see, for example, Smith, EP 405781).

MTBE serves primarily to increase the octane number of transportgasoline. MTBE and IBTBE can alternatively be dissociated over acidicoxides in the gas phase at from 150 to 300° C. to obtain pure isobutene.

To prepare isovaleraldehyde in step c.2, the b-C₄ fraction is convertedtogether with synthesis gas. The configuration of the process isgenerally known and is described, for example, in J. Falbe: NewSyntheses with Carbon Monoxide, Springer Verlag, Berlin Heidelberg NewYork 1980, Chapter 1.3. Co-complexes in particular have proven useful ascatalysts. For instance, the catalyst used in the BASF process isHCO(CO)₄ in aqueous solution and is reacted with the substrate in a loopreactor.

Polyisobutylene is prepared in step c.3 generally over acidichomogeneous and heterogeneous catalysts, for example tungsten trioxideon titanium dioxide or boron trifluoride complexes. In this way, aneffluent stream can be obtained at isobutene conversions of up to 95%which has a maximum residual isobutene content of 5%.

The preparation of high molecular weight polyisobutylene havingmolecular weights of 100 000 and more is described, for example, in H.Guterbock: Polyisobutylen und Mischpolymerisate, p. 77 to 104, SpringerVerlag, Berlin 1959.

Low molecular weight polyisobutylenes having a number-average molar massof from 500 to 5000 and a high content of terminal vinylidene groups andtheir preparation are disclosed, for example, by DE-A-2702604, EP-A-628575 and WO 96/40808.

In the alkylation of step c.5, the b-C₄ fraction is reacted withbranched saturated hydrocarbons having 4 or 5 carbon atoms. This formsmainly branched saturated hydrocarbons having 8 or 9 carbon atoms whichare used mainly as a fuel additive for improving the octane number. Thecatalysts used in the reaction are typically hydrofluoric acid orsulfuric acid.

1. A process for preparing oligomers consisting mainly of repeatingunits derived from 1- or 2-butene from a hydrocarbon stream consistingsubstantially of branched and linear hydrocarbon compounds having 4carbon atoms, and comprising olefinic branched and linear hydrocarboncompounds having 4 carbon atoms (C₄ starting stream) by; a. separatingthe C₄ starting stream into a fraction consisting mainly of linearhydrocarbon compounds having 4 carbon atoms (l-C₄ fraction) and afraction consisting mainly of branched hydrocarbon compounds having 4carbon atoms (b-C₄ fraction), by contacting the C₄ starting stream witha membrane which is easier to pass for linear hydrocarbon compoundshaving 4 carbon atoms than for branched carbon compounds having 4 carbonatoms; b. optionally after removing butanes, oligomerizing the olefinichydrocarbon compounds having 4 carbon atoms present in the l-C₄fraction; c. subjecting the olefinic hydrocarbon compounds having 4carbon atoms present in the b-C₄ fraction to one of the following steps:c1. reaction with methanol to give methyl tert-butyl ether; c2.hydroformylation to give substantially isovaleraldehydel; c3.polymerization to polyisobutylene; c4. dimerization to2,4,4-trimethyl-1-pentene; and c5. alkylation, substantially to formsaturated hydrocarbon compounds having 8 or 9 carbon atoms.
 2. A processas claimed in claim 1, wherein the membrane used is made of inorganicmaterial having molecular sieve properties.
 3. A process as claimed inclaim 1, wherein the membrane used consists at least partly of zeolitesof the MFI type.
 4. A process as claimed in claim 1, wherein theseparation in step a) is carried out in such a way that the C₄ startingstream in liquid or gaseous form is contacted with the membrane and thel-C₄ fraction passing the membrane is removed in gaseous form, and thepressure on the side of the membrane on which the C₄ starting stream isdisposed is greater than the pressure on the side of the l-C₄ fraction.5. A process as claimed in claim 1, wherein the C₄ starting stream usedconsists substantially of; from 30 to 99% by weight of olefinic branchedand linear hydrocarbon compounds having 4 carbon atoms; optionally from1 to 70% by weight of saturated branched and linear hydrocarboncompounds having 4 carbon atoms; and optionally up to 50% by weight ofany other unsaturated hydrocarbon compounds having 4 carbon atoms; andoptionally from 0 to 50% by weight of any hydrocarbon compounds havingless than 4 or more than 4 carbon atoms.
 6. A process as claimed inclaim 5, wherein the C₄ starting stream is prepared by carrying out thefollowing sequence of steps: removing a C₄ hydrocarbon fraction (C₄stream) from a hydrocarbon stream from natural sources or obtainable bysubjecting naphtha or other mixtures which consist essentially ofhydrocarbons to a steam cracking or FCC process; preparing a C₄hydrocarbon stream consisting substantially of isobutene, 1-butene,2-butene and butanes (raffinate l) from C₄ stream by hydrogenating thebutadienes and butynes to C₄-alkenes or C₄-alkanes by means of selectivehydrogenation or removing the butadienes and butynes by extractivedistillation; and freeing raffinate l of catalyst poisons by treatingwith adsorbent materials and in this way obtaining C₄ starting stream.7. A process as claimed in claim 1 any of claims 1, wherein, in step b,the l-C₄ fraction is converted mainly to octenes and dodecenes over anickel catalyst.
 8. A process as claimed in claim 1, wherein, in step b,the removal of butanes is effected distillatively.
 9. A process asclaimed in claim 7, wherein the octenes or dodecenes are converted tononanol or tridecanol by hydroformylation and subsequent hydrogenation.